WO2019103447A1

WO2019103447A1 - Electrode assembly having improved safety of use by means of structure in which local site in exterior material is reinforced with elastic polymer film, and lithium-ion secondary battery having same

Info

Publication number: WO2019103447A1
Application number: PCT/KR2018/014331
Authority: WO
Inventors: 김주성; 하진홍; 이길주
Original assignee: 주식회사 리베스트
Priority date: 2017-11-23
Filing date: 2018-11-21
Publication date: 2019-05-31
Also published as: KR101937185B1; US20200358043A1

Abstract

A secondary battery, according to the present invention, comprises: an electrode assembly; and an exterior material for covering the outer side of the electrode assembly by having a structure in which top stamped portions and bottom stamped portions are repeatedly stamped. The top stamped portions and the bottom stamped portions form a corrugated pattern. The electrode assembly comprises: at least one unit cell having a pair of electrode plates having different polarities from each other and having a separator interposed therebetween; an electrode mixture applied on one surface or both surfaces of the pair of electrode plates; and an electrode tab protruding from each of the electrode plates while at the same time, being in a state where the electrode mixture is not applied thereon. The electrode tab includes an electrode parallel connecting tab and an electrode lead connecting tab. The electrode plates have formed thereon at least one electrode tab among the electrode parallel connecting tab and the electrode lead connecting tab. A structure is formed in which a local site of the exterior material is reinforced with an elastic polymer film thereon.

Description

An electrode assembly having improved stability in use through a structure for reinforcing an elastic polymer film at a local site within the casing, and a lithium ion secondary battery

In order to prevent the risk of ignition or explosion caused by the breakage of the casing and the internal short circuit, which may occur due to bending and torsion, which is a repetitive external force in a flexible environment, The elastic polymer film is reinforced on the local part in the case member abutting on the assembly so as to cut the outermost electrode having the electrode lead connecting tab and the parallel connecting tab before the breakage or internal short- And to ensure safety in use by inducing them.

A secondary battery is a battery capable of charging and discharging unlike a primary battery which can not be charged, and is widely used in high-tech electronic devices such as a cellular phone, a notebook computer, and a camcorder. [0003] As the portable electronic devices have become lighter and more sophisticated and the Internet of things (IOT) has developed, much research has been conducted on secondary batteries used as driving power sources.

Particularly, lithium secondary batteries have higher voltage and higher energy density per unit weight than nickel-cadmium batteries and nickel-hydrogen batteries, which are widely used as power sources for portable electronic equipment, and their demand is increasing.

The secondary battery is a battery using an electrochemical reaction generated between an electrolytic material and an electrode when the positive electrode and the negative electrode are connected to each other while an anode and a cathode are inserted into the electrolytic material. Unlike a conventional primary battery, Is a battery capable of recharging and recharging the energy consumed by the battery charger and used repeatedly, so that it is spreading with the popularization of wireless electric and electronic products.

Typically, a flexible laminate type electrode assembly formed by laminating a plurality of positive electrode plates and negative electrode plates with a separator interposed therebetween is formed by inserting a separation membrane between a positive electrode plate and a negative electrode plate and winding them together in a spiral shape, It is widely used in secondary batteries. For example, a cylindrical battery includes a cylindrical can accommodated in a cylindrical can, and an electrolyte is injected and sealed. The prismatic type cell is formed by pressing a wound electrode assembly or a stacked electrode assembly to flatten and flatten it, . The pouch-type battery is formed by wrapping a wound electrode assembly or a stacked electrode assembly together with an electrolyte in a pouch-type sheathing material. In such an electrode assembly, the positive electrode tab and the negative electrode tab may be respectively drawn out from the positive electrode plate and the negative electrode plate to the outside of the electrode assembly and connected to the positive electrode and the negative electrode of the secondary battery.

On the other hand, the existing pouch-type lithium secondary battery is damaged due to intentional external force applied to the outer surface of the lithium secondary battery, so that electrolyte leakage and external air inflow into the exterior material occur. Such leakage of the electrolyte hinders normal operation such as corrosion of peripheral components such as a battery protection circuit. Further, it causes a great safety problem such as ignition due to inflow of outside air.

As a method for improving the durability of the lithium secondary battery, by forming the exterior material pattern constituting the secondary battery by lithium and improving the durability of the battery by applying the terminal reinforcing structure, the battery can be stably electrochemically actuated for bending and twisting, .

On the other hand, in a flexible environment, there may be a risk of ignition or explosion due to breakage of the casing due to repeated bending and twisting, and short circuit due to misalignment and deviation of internal electrodes. The internal short circuit is caused by excessive current flowing in proportion to the area where the anode and the cathode are in contact with each other. In such a case, a secondary short circuit may be additionally generated and there is a risk of ignition and explosion.

In general, the structure of the battery is connected externally to all the electrodes in the case of a winding type or a general laminated battery, so that an internal short circuit occurs when the electrodes and the separator are damaged due to an external impact.

When the internal short circuit occurs as described above, even if the internal electrode or the outermost electrode, which may be a part of the electrode assembly, is cut off, there is a problem that the capacity is reduced. However, There is no problem in the operation of the battery. However, there is a serious problem in safety when the internal electrode is continuously used in the breakage and disconnection state.

Korean Patent Application Publication No. 10-2016-0090104 discloses an electrode assembly for a flexible battery, in which an electrode assembly included in an existing pouch-shaped battery has a problem in that when an external force is applied to the electrode assembly, A reinforcing member is provided on one surface of an assembly to prevent breakage even when an external force is applied.

(Patent Document 1) KR10-2016-0090104 A

SUMMARY OF THE INVENTION [0011] Accordingly, an object of the present invention is to provide an electrode assembly for a battery, which has a structure in which an elastic polymer film is reinforced on a local site in a case member contacting with an electrode assembly constituting a battery, It is another object of the present invention to provide a structure for securing safety in use by inducing cutting of an outermost electrode provided with a tab for use.

According to an aspect of the present invention, there is provided a lithium ion secondary battery comprising: an electrode assembly; And a sheathing structure in which the upper and lower stamping portions are formed in a repetitive shape so as to surround the outer surface of the electrode assembly, wherein the upper stamping portion and the lower stamping portion form a wrinkle pattern, At least one unit cell having a pair of electrode plates having different polarities at a predetermined interval; An electrode material mixture applied on one or both surfaces of the pair of electrode plates; And electrode tabs protruding from the electrode plates and not yet coated with the electrode mixture, wherein the electrode tabs include tabs for electrode parallel connection and tabs for electrode lead connection, The electrode tabs for connecting the electrodes in parallel and the tabs for connecting the electrode leads are formed, and the elastic polymer film is reinforced on the local area between the electrode assemblies contacting the case.

The local portion X reinforced by the elastic polymer film is 1/15 to 1/3 of the total length L of the casing.

The shore hardness of the elastic polymer film is 30 to 80 (shore A, A type).

The elastic polymer film may be any one selected from the group consisting of unsaturated rubbers that can be cured by sulfur vulcanization, saturated rubbers can not be cured by sulfur vulcanization and thermoplastic elastomers. Or more.

Wherein the electrode assembly includes an outermost negative electrode plate disposed at an outermost periphery and an outermost positive electrode plate integrally disposed inside the outermost negative electrode plate, wherein the outermost negative electrode plate and the outermost positive electrode plate each have an electrode- Includes all connection tabs.

The electrode assembly further includes a reinforcing tab welded and fixed on one of the electrode tabs of the electrode tabs constituting the electrode assembly.

The electrode assembly may be bent in a direction opposite to the electrode assembly by 180 ° in a state where the electrode leads are coupled to one of the electrode lead connecting tabs of the electrode tabs forming the electrode assembly so as to face the electrode assembly. And further includes an outwardly directed bending structure.

And the tab lead connecting portions of the electrode lead connecting tabs and the electrode leads are padded by using the reinforcing tabs are inserted and aligned inside the separating film.

The tab-and-lid coupling portion, in which the electrode lead connecting tab and the electrode lead of the bending structure are coupled, is inserted and aligned inside the separating membrane.

The outermost negative electrode plate disposed at the uppermost and lowermost ends of the electrode assembly is coated with an electrode mixture.

According to the present invention, when tensile stress and compressive stress due to external bending are repetitively applied to an electrode assembly, the outermost electrode portion, which faces a part of the exterior material having a locally formed elastic polymer reinforcing film, And the bending causes the stress to act locally more severely than the other portions, and the current is cut off by the structure, thereby disabling the function of the battery and ensuring safety in use.

In addition, as the charging / discharging progresses, the electrode expands and shrinks in volume. In the portion of the exterior material where the elastic polymer reinforcing film is formed, the portion facing the area is repeatedly subjected to repeated bending and bending, It is locally severe compared to other parts.

A process in which when the outermost electrode having both the electrode lead connecting tab and the parallel connecting tab is cut off, the only passage in which the electrons in the active material are connected to the outside is cut off, To ensure safety in use.

The outermost electrode and the common electrode constituting the electrode assembly according to the present invention are connected by a tab for parallel connection, and a terminal is formed on the tab portion for connecting the electrode lead on the outermost electrode. When external force such as bending and twisting is applied The outermost electrode is preferentially damaged and cut. At this time, when the outermost electrode provided with the electrode lead connecting tab is disconnected, the normal electrodes connected by the parallel connection tab are shut off in the state of the current being cut off, It does not function.

1 shows an exemplary configuration of an electrode assembly constituting a flexible battery according to the present invention.

FIGS. 2 and 3 show an exploded view of an electrode assembly in which an outermost electrode is disposed as a cathode according to an embodiment of the present invention.

Fig. 4 shows a state in which a casing having a corrugated pattern reinforced by an elastic polymer film surrounds the outer periphery of the electrode assembly.

5 shows a state where a general exterior material having a flat pattern reinforced with an elastic polymer film surrounds the outer periphery of the electrode assembly.

6 shows a state in which other internal electrodes constituting the electrode assembly are set to a closed state (shutdown) due to the occurrence of cutting on the outermost battery.

7 shows a flexible battery having an electrode assembly and a cover member surrounding the electrode assembly.

8 shows a state in which a pattern such as an upper pressing portion and a lower pressing portion is formed in a direction parallel to the width of the exterior material portion in the exterior material portion constituting the flexible battery.

FIG. 9 illustrates a specific shape of the upper and lower pressing portions formed on the casing member.

Fig. 10 shows the result of bending evaluation of the case where the elastic polymer film is locally reinforced with a wrinkle pattern according to the present invention and other comparative examples.

Hereinafter, a flexible battery according to the present invention will be described with reference to the accompanying drawings.

The following examples are intended to illustrate the present invention and should not be construed as limiting the scope of the present invention. Accordingly, equivalent inventions performing the same functions as the present invention are also within the scope of the present invention.

In addition, in adding reference numerals to the constituent elements of the respective drawings, it should be noted that the same constituent elements are denoted by the same reference numerals even though they are shown in different drawings. In the following description of the present invention, a detailed description of known functions and configurations incorporated herein will be omitted when it may make the subject matter of the present invention rather unclear.

1 to 3, an electrode assembly according to an embodiment of the present invention, which improves stability in battery usage through cutting induction of an outermost electrode facing a partial area of a facing material formed with a locally elastic polymer reinforcing film, Explain.

The electrode assembly includes a unit cell (A) divided into an anode plate (10) and a cathode plate (20) with a separator (30) therebetween, an electrolyte solution serving as an ion transfer medium between the anode plate and the anode plate, And an electrode tab for dividing the electrode for connecting the electrode to the parallel connection. Any one or more of the electrode plates including the negative electrode plate 10 and the positive electrode plate 20 may be disposed on both sides of the tab for electrode parallel connection and the tab for electrode lead connection. For example, the outermost negative electrode plate 10 disposed at the lowermost end of the electrode assembly 100 includes the negative electrode parallel connection tab 12 and the negative electrode lead connection tab 14, An optional positive electrode plate disposed on the upper side has a tab 22 for connecting the positive electrode and a tab 24 for connecting the positive electrode lead. That is, at the lowermost end of the electrode assembly, the negative electrode and the positive electrode having both the tab for connecting parallel electrodes and the tab for connecting the electrode leads are integrally disposed.

Here, the electrode plates are coated on the end surface or both surfaces of the electrode plate as the electrode current collector, and the tabs for electrode parallel connection and the tabs for connecting the electrode leads protrude from the electrode plate. On the other hand, the tabs for electrode-parallel connection and the tabs for connecting the electrode leads are exposed in an uncoated state.

The plurality of electrode plates are connected to each other through the electrode tabs for electrode parallel connection. That is, the plurality of negative electrode plates 10 and the plurality of positive electrode plates 20 are electrically connected in parallel by the tab-to-tab joints connecting the electrode tabs.

Meanwhile, the electrode assembly has a structure that is electrically connected to the electrode lead exposed to the outside of the casing through the electrode lead connecting tab. The separation membrane physically separates the electrode plates, but functions to pass ions contained in the electrolytic solution.

The negative electrode plate disposed at the uppermost and lowermost ends of the electrode assembly may be in a state in which the negative electrode mixture 40 is applied only on the end face.

The electrode-

parallel connection tabs

12 and 22 protruding from the cathode plate 10 or the positive electrode plate 20 are electrically connected in parallel by electrode plates having the same polarity. The tab-to-tab joints connected in parallel are positioned on the separation membrane that surrounds the outer surface of the outermost electrode plate forming the uppermost or lowermost end of the electrode assembly, and subjected to finish taping.

In the present invention, the connection between the tab-to-tab connecting portion and the electrode lead connecting tabs (14, 24) connected in parallel to each other and the tab-to-lead connecting portion where the electrode leads are connected to each other And bonding are electrically connected through any of bonding methods including spot welding, ultrasonic welding, laser welding, and bonding by a conductive adhesive.

The electrodes disposed at the uppermost and lowermost ends of the electrode assembly are all negative electrodes, but this is not limitative. In the present invention, the uppermost and lowermost electrodes may be disposed in the electrode assembly in combination of any one of a cathode / a cathode, a cathode / an anode, a cathode / an anode, and an anode / an anode.

The electrode assembly according to the present invention can reinforce a separate reinforcing tab on the electrode lead connecting tabs (14, 24) disposed on one side of the electrode assembly. By joining the electrode leads to the reinforcing tabs, the electrode lead connecting tabs (14, 24) and the electrode leads are formed by using the reinforcing tabs. The reinforcing bonding method for bonding the electrode lead connecting tabs (14, 24) to the electrode leads using the reinforcing tab corresponds to at least one of the positive electrode tab and the negative electrode.

The reinforcing tab is physically reinforced by reinforcing the strength of the connection portion between the electrode lead connecting tabs (14, 24) and the electrode lead. Illustratively, the same or different kinds of metal reinforcing tabs, which are 1 to 5 times thicker than the tabs for connecting the electrode leads, are welded to the upper ends of the tabs for electrode lead connection extending from the electrode plate of the electrode assembly. The reinforcing tabs reinforced by the overhang and the tabs for connecting the electrode leads have the same or different widths. The width of the reinforcing tab to be reinforced may be 3 to 5 mm and the length may be 2 to 4 mm, but this is not limitative.

The electrode leads, which are joined to the electrode lead connecting tabs by being bonded onto the reinforcing tabs reinforced by the overhang, may have a width of 2 mm to 3 mm and a length of 0.5 mm to 1 mm, But is not limited to. In the present invention, the current collector of the electrode plate may be any one of a group including aluminum, stainless steel, and copper, and the electrode lead may have any one material selected from the group consisting of aluminum, nickel, and nickel coated with nickel have. The tab for electrode lead connection and the reinforcing tab for reinforcing by the overlay on the tab lead connection portion of the electrode lead are formed in one of the group including circle, ellipse and polygon.

Meanwhile, the electrode assembly according to the present invention may have a structure in which the electrode lead bending structure is coupled to the

tabs

14 and 24 for connecting the electrode leads.

A part of the end of the electrode lead is welded to the upper end of the electrode lead connecting tab in a state where the electrode lead is arranged in parallel to the top of the electrode lead connecting tab. In this state, the electrode leads are bent from the electrode lead connecting tabs toward the outer side of the electrode assembly through the process of bending the electrode leads 180 degrees. This is characterized by a joint reinforcing structure between the electrode tabs and the electrode leads by minimizing the local mechanical load in a flexible environment.

The electrode lead connecting tabs and the electrode leads may be bonded to each other by bending. The width of the electrode leads connected to the tabs for connecting the electrode leads may be 2 mm to 3 mm, The length may be from 1 mm to 3 mm, but this is not limitative.

The electrode

lead connecting tabs

14 and 24 and the tab-and-lid connecting portion formed by combining the electrode leads with reinforcing tabs or the tab-and-lid connecting portion having the electrode lead connecting tabs and the bend tab- As shown in FIG. This protects the flexible battery by preventing external exposure of the terminal part, which is the weakest point of the flexible battery.

4 shows a state in which a casing having a corrugated pattern reinforced by an elastic polymer film surrounds an outer periphery of the electrode assembly according to the present invention.

The elastic polymer reinforcing film 240 having an elastic property can be disposed on the entire length L of the covering member 200 on the covering member 200 surrounding the outer surface of the electrode assembly 100.

The elastic polymer reinforcing film 240 is disposed in such a manner that the elastic polymer reinforcing film 240 is thermally compressed on the bony portion of the facer material 200 having a wrinkled pattern. The elastic polymer reinforcing film 240 may be thermocompression bonded to all the valley portions along the longitudinal direction of the casing member 200 or alternatively.

The length X of the local region where the elastic polymer film is reinforced is set to 1/15 to 1/3 of the total length L of the covering member and the width Y of the local region is preferably equal to the width of the electrode plate inside the electrode assembly. This is because it is possible to effectively induce the cutting of the outermost electrode by the binding force in the facings determined according to the size of the elastic polymer film reinforcing portion and the bending applied from the outside.

The width Y of the elastic polymer film reinforcement portion should not invade the sealing portion of the casing so that the stability of the battery such as electrolyte leakage and external air inflow due to damage of the sealing portion during sealing of the casing is not threatened.

When the length X of the elastic polymer film reinforcement portion is less than 1/15 of L, it is not possible to effectively cut the outermost electrode and it is not easy to reinforce the elastic polymer film by thermocompression on the casing material.

On the other hand, if it exceeds 1/3 of the length L of the casing, the stress is dispersed due to repetitive warpage and bending due to its wide range, which makes it difficult to induce effective cutting of the outermost electrode.

The elastic polymer reinforcing film 240 may be SEBS (Styrene-Ethylene-Butylene-Styrene, TPR).

The elastic polymer reinforcing film may be one selected from the group consisting of unsaturated rubbers that can be cured by sulfur vulcanization, saturated rubbers can not be cured by sulfur vulcanization, and thermoplastic elastomers. Or more.

In the case of vulcanized unsaturated rubbers, natural polyisoprene (cis-1,4-polyisoprene (Natural rubber), trans-1,4-polyisoprene (Gutta-percha)), polyisoprene rubber (IR), polybutadiene rubber CR), Neoprene, Bayprene etc., Poly (isobutyleneco-isoprene) rubber IIR, Chloro IIR, Bromo IIR, Poly (styreneco-butadiene) rubber (SBR), Poly (acrylonitrile- ) rubber (NBR), Hydrogenated NBR (HNBR), Therban, and Zetpol.

Polyacrylic rubber (ECM), polyacrylic rubber (ACM, ABR), Silicone rubber (SI, Q, VMQ), Fluorosilicone rubber (FVMQ), Polyether block amides (PEBA), Chlorosulfonated polyethylene Hypalon, and Ethylene-vinyl acetate (EVA).

In the case of thermoplastic elastomeric polymers, there are thermoplastic styrenic block copolymers (TPE-s), for example, polystyrene-blockpolybutadiene-block-polystyrene (SBS), polystyrene-block-polyisoprene-blockpolystyrene (ethylene-ran-propylene) -blockpolystyrene (SEPS), polystyrene-block-poly (ethylene-ran-butylene) -blockpolystyrene (SEBS) and the like.

Other thermoplastic elastomeric polymers and olefin polymer blends are known as thermoplastic polyolefin blends (TPE-o). This polymer is an elastomeric alloys of TPE-s and polyolefin such as PS, PP and PE as described above such as SBS, SIS, SEPS, SEBS and the like. Other thermoplastic elastomeric polymers include thermoplastic polyurethanes (TPU), thermoplastic copolyester, and thermoplastic polyamides.

Finally, in the case of thermoplastic vulcanizate elastomer (TPV), there are ethylene propylene monomer (EPM) rubber, ethylene propylene dienemonomer (EPDM) rubber, fluroelastomer (FKM, and FEPM) and perfluoroelastomers (FFKM).

The Shore hardness of the elastic polymer reinforcing film 240 is 30 to 80 (Shore A, A Type). Hardness refers to the magnitude of resistance to deformation of an object when it is pressed by another object. It is largely divided into Vickers hardness, Brinell hardness, Rockwell hardness, Shore hardness and the like. In the case of the above elastic polymer, it is measured and indicated by Shore hardness. The Shore hardness tester is a type of indenter which is classified into A, B, C, D, OO, etc. according to the shape of the indenter. The elastic polymer reinforcing film 240 is preferably of the A type of 30 to 80. If the elastic polymer reinforcing film 240 is less than 30, it is difficult to effectively cut the outermost electrode in the electrode assembly due to its low hardness. In an operation such as bending or twisting exceeding 80 degrees It is difficult to damage the exterior material and the electrode assembly and to exhibit the normal performance of the flexible battery.

FIG. 5 is a comparative example of an embodiment according to the present invention, in which a general exterior material having a flat pattern reinforced with an elastic polymer film surrounds the outer periphery of the electrode assembly.

FIG. 6 shows a state where other internal electrodes constituting the electrode assembly are set to a closed state (shutdown) due to the occurrence of cutting on the outermost cell according to the present invention.

Specifically, a plurality of cells constituting the electrode assembly are connected to each other through right-side parallel connection tabs, and a terminal is formed at an electrode lead connecting tab portion on an electrode plate disposed at the outermost part of a lower end of the plurality of cells.

In this state, when an external force such as bending and twisting is applied to the electrode assembly from the outside, the electrode at the outermost part of the lower end of the electrode assembly is preferentially damaged and cut, rather than the inside of the electrode assembly.

At this time, if the outermost electrode provided with the electrode lead connecting tab is broken, the electrodes connected by the parallel connection taps are cut off and become closed, and the capacity is reduced and the battery is not functioned . This provides a function to prevent the internal electrode from being differentiated from the existing battery which has a risk of ignition that may occur due to an internal short circuit when continuously used even when the internal electrode is damaged.

To this end, the present invention appropriately utilizes the types and arrangements of the outermost electrodes to induce the cutting of the electrodes provided with the electrode lead connecting tabs before the appearance of the casing or the occurrence of an internal short circuit. Such an intended structure can be applied to a device that requires a safety and control of the performance of the flexible battery at a certain number of bend times or more due to external force, while securing the battery from the risk of carelessness or excessive bending.

Referring to FIG. 7, the electrode assembly according to the present invention disposes the outer casing part 200 of the processed structure, which is formed by repeatedly pressing the upper and lower pressing parts to surround the outer surface of the electrode assembly.

Referring to Fig. 8, the pattern and shape are repeated so that a plurality of upper crimping portions and lower crimping portions repeatedly crimped on the casing member can be compressed and tensioned in a flexible battery having an electrode assembly in a bending, twisting, or wrinkling operation .

The plurality of upper crimping portions and the lower crimping portion are continuously formed in a direction parallel to the widths of the electrode assembly and the covering member.

The plurality of upper crimp portions and the lower crimp portions are each crimped to the upper and lower molds.

The outer covering member surrounding the outer surface of the electrode assembly may have an upper casing member 210 and a lower casing member 220 on the electrode assembly with reference to a red dotted line of the sealing member 230. That is, the plurality of

upper depression portions

212 and 222 and the

lower depression portions

214 and 224 repeated on the casing member are formed symmetrically with respect to the ceiling portion, and the upper and

lower casing members

210 and 210 220). &Lt; / RTI > In this state, the electrode assembly is housed in the exterior member after the sealing portion is bent symmetrically upward and downward.

The width of the sealing portion, which is a reference for separating the upper and

lower casing members

210 and 220, may be 3 mm to 5 mm and the actual sealing width may be 1 mm to 2 mm, But is not limited to.

Referring to FIG. 9, a plurality of repeated upper and lower heights h and h 'may be the same (h = h') on the outer casing.

A plurality of upper and lower repetition portions h and h 'are 0.5 mm to 1 mm and an optimum value is 0.75 mm. However, the present invention is not limited thereto.

The thickness of the elastic polymer film thermocompression-bonded by the sub-height h and the sub-height h ', which are the upper and lower pressures formed on the casing, is determined to be 0.5 mm to 1 mm, It is not.

If the thickness of the elastic polymer film is less than 0.5 mm, it is impossible to effectively cut the outermost electrode. If the thickness exceeds 1 mm, a high pressure is applied to the electrode assembly and the casing by the elastic polymer film reinforcement, The outermost electrode is cut off due to damage or breakage such as wrinkling of the casing, so that an overvoltage is instantaneously applied, which makes flexible and normal electrochemical driving difficult.

On the other hand, the width (a) between the plurality of upper peak portions of the upper shell and the width (b) between the lower peak portions of the lower peak portions adjacent to each other on the casing member are the same (a = b) to form a wave pattern.

The present invention is characterized in that a cathode is disposed on an outermost electrode of an electrode assembly having a plurality of electrodes stacked vertically through a separation membrane to prevent breakage of the electrode terminal when the flexible battery is bent.

The uppermost graph in FIG. 10 shows an embodiment according to the present invention. There is no corrugation of the casing and damage to the sealing portion after the bending evaluation, but it can be confirmed that the outermost electrode is cut at about 2,000 bend times.

Specifically, as an example according to the present invention, when a cell having an elastic polymer reinforcing film is locally provided in a casing having a corrugated pattern formed therein, the outermost electrode is cut at about 2,000 times, And the bending durability is much better than that of Comparative Example 1 which is the lowermost graph.

It can be seen that the force is continuously concentrated on the outermost electrode facing the locally formed elastic polymeric reinforcing film in the facer having the wrinkle pattern, leading to cracking of the compound layer crack of the outermost electrode and cutting of the current collector.

10 shows a comparative example 1 in which a general exterior material having a flat pattern reinforced with an elastic polymer film surrounds the outer periphery of the electrode assembly as shown in Fig.

In the comparative example 1, both the damage of the casing and the cutting of the outermost electrode are performed.

In the case of the comparative example 1, when the bending evaluation of 25 cpm (25 times / minute) is performed, it is confirmed that the casing material damage and the outermost electrode are cut off in less than 100 times and the voltage suddenly surges due to the sudden increase.

Although the input current is constant, the outermost electrode is disconnected, and the common electrodes connected by the parallel connection taps are shut down in the state where the current is shut off, so that the capacitance is sharply reduced, It is caused by the phenomenon that the overvoltage suddenly increases while it is getting larger. In the case of a general battery, all the electrodes are bound together to be connected to the outside. However, since the present invention has a single electrode having a current path for current flowing to the outside of the cell, that is, an electrode lead connecting tab, Disconnection of the battery occurs.

In FIG. 10, the graph at the center indicates Comparative Example 2, and it can be confirmed that no damage is caused to the casing and the cutting of the outermost electrode does not occur. On the other hand, both the electrode and the casing are damaged at a bending frequency of 8,000 times or more.

Comparative Example 2, which is a general flexible battery, has a high probability of occurrence of an internal short circuit due to breakage of the casing or lithium precipitation about 8,000 times of repetitive bending cycles.

The present invention introduces a sheath having a flat pattern reinforced with an elastic polymer film before the occurrence of a short circuit or the like, thereby inducing the outermost electrode to be cut first by intentionally less than 8,000 times.

As a result of a number of experiments as described above, a local elastic polymer reinforcing film is formed in a casing having a wrinkle pattern to cause electrode cutting at a local site and disconnection of the battery at a frequency of about 1,500 to 2,500 times, It is possible to design the damage and cutting of the outermost electrode intentionally before the number of times of excessive bending which is high in probability of occurrence of an internal short circuit due to lithium precipitation, thereby securing safety in battery usage.

The present invention is characterized in that when the tensile stress and the compressive stress due to external bending are repeatedly applied to the electrode assembly, the outermost electrode portion, which is partially opposed to a portion of the sheath where the elastic polymer reinforcing film is locally formed, is subjected to repetitive bending and bending The stress is applied locally more severely than the other parts, so that the current is cut off due to the cut off, thereby making it possible to secure the safety of the battery by disabling the function of the battery from the risk of carelessness or excessive bending .

The present invention can be used in a flexible lithium ion secondary battery.

Claims

An electrode assembly; And

And an outer casing surrounding the outer surface of the electrode assembly,

The electrode assembly includes:

At least one unit cell having a pair of electrode plates having different polarities with a separator interposed therebetween;

An electrode material mixture applied on one or both surfaces of the pair of electrode plates; And

And electrode tabs protruding from the electrode plates, respectively,

Wherein the electrode tab includes an electrode-parallel connection tab and an electrode lead connection tab,

Wherein the electrode plate is formed with at least one of the electrode-parallel connection tab and the electrode lead connection tab,

And an elastic polymer film is bonded to the electrode assembly on a local area of the inner surface of the casing.
The method according to claim 1,

And the length X of the portion where the elastic polymer film is bonded is 1/15 to 1/3 of the total length L of the casing.
The method according to claim 1,

Wherein the elastic polymer film has a Shore hardness of 30 to 80 (Shore A, A Type)
The method according to claim 1,

The elastic polymer film may be any one selected from the group consisting of unsaturated rubbers that can be cured by sulfur vulcanization, saturated rubbers by cured by sulfur vulcanization, and thermoplastic elastomers. Or more.
The method according to claim 1,

Wherein the electrode assembly includes an outermost negative electrode plate disposed at an outermost periphery and an outermost positive electrode plate disposed adjacent to the outermost negative electrode plate in a face-

Wherein the outermost negative electrode plate and the outermost positive electrode plate are formed with tabs for connecting parallel electrodes and tabs for connecting electrode leads, respectively.
The method according to claim 1,

The electrode assembly includes:

And a reinforcing tab coupled to the tab for connecting the electrode lead.
The method according to claim 1,

Wherein the electrode lead includes:

And a bending structure formed on the electrode lead connecting tab so as to bend in a direction toward an outer side of the electrode assembly at a side facing the electrode assembly.
The method according to claim 6,

And the tab lead engaging portion padded by the reinforcing tab is inserted into the separating film.
8. The method of claim 7,

Wherein the tab-lead coupling portion, in which the electrode lead connecting tab and the electrode lead of the bending structure are coupled, is inserted into the separator.
The method according to claim 1,

And the outermost negative electrode plate disposed at the uppermost and lowermost ends of the electrode assembly is coated with an electrode mixture.
The method according to claim 1,

The exterior material has a repeated upper and lower depressions,

Wherein a width Y of the elastic polymer film is smaller than a width between sealing portions formed at both ends of the casing, in a direction in which the upper crimp portion and the lower crimp portion extend.
The method according to claim 1,

The exterior material has a repeated upper and lower depressions,

Wherein a width Y of the elastic polymer film is equal to a width of the electrode plate in a direction in which the upper and lower depressions extend.
The method according to claim 1,

The exterior material has a repeated upper and lower depressions,

Wherein the elastic polymer film is thermocompression-bonded to the valley portion formed by the upper tack portion and the lower tack portion.